JP2005052888A - Thin al-cu joined structure, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin Al-Cu joined structure of excellent dimensional characteristic by ensuring an Al-Cu different joining member of excellent workability, and reducing the thickness thereof by rolling. <P>SOLUTION: (1) In the thin Al-Cu joined structure, a brazed member with Ag used for an insert on a joining surface of an Al member with a Cu member is rolled. The thin Al-Cu joined structure is ≥ 0.1 mm thick, and the thickness of the brazed member is preferably reduced by the hot-rolling. (2) In the method for manufacturing the thin Al-Cu joined structure, rolling is performed with the brazed member with Ag used for the insert on the joining surface of the Al member with the Cu member as a starting material. In the method for manufacturing the thin Al-Cu joined structure, the hot-rolling is performed at the temperature of 350-500°C, the draft at each rolling is set to be 20%±10% when the hot-rolling is repeated, and annealing is preferably performed after finishing the hot-rolling. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention comprises an aluminum or aluminum alloy (hereinafter collectively referred to as “Al (aluminum)”) member and a copper or copper alloy (hereinafter collectively referred to as “Cu (copper)”) member. The present invention relates to a thin joint structure and a manufacturing method thereof.

  More specifically, a brazed joint member using silver or a silver alloy (hereinafter collectively referred to as “Ag”) as an insert material is rolled on the joint surface between the Al member and the Cu member, and preferably hot The present invention relates to a thin Al—Cu bonded structure capable of exhibiting excellent dimensional characteristics by rolling and a manufacturing method thereof.

  Heat exchangers, radiators, heat pipes, heat sinks, and the like used as electronic devices and communication devices, and also as transportation devices such as automobiles and airplanes are required to have a light weight as well as excellent heat transfer performance. Therefore, as a material for heat exchange or heat transfer, it is lightweight and replaces Cu (copper), which has excellent heat transfer and thermal diffusibility, but is difficult in terms of weight reduction. Al (aluminum) is widely used.

  In particular, Al heat exchangers used in electronic equipment have been improved by increasing the cooling area and increasing the material thickness in order to improve heat transfer performance. Miniaturization, thinning, weight reduction, and high performance become remarkable, and there is a limit to improvement of heat transfer performance on the extension line of these improvements.

  In light of such a technical background, in consideration of the excellent heat transfer and corrosion resistance of Cu and the lightness of Al, while suppressing the increase in weight to less than Cu, Al- Development of a structure having a Cu joint is desired.

  Conventionally, application of solid phase bonding methods such as diffusion bonding, friction welding, and explosive bonding has been studied with respect to bonding of dissimilar materials of Al and Cu, and some bonding methods have been put into practical use. However, these joining methods make it difficult to join large areas and complex shapes, and there are limitations on the shape and dimensions of the joined body, and it is difficult to apply to precision parts typified by electronic devices.

  On the other hand, brazing is a technique that has been widely used as a metal joining method, and is simple and has a high degree of freedom in materials to be joined, so that it can be easily applied to precision parts. However, in brazing bonding of Al—Cu, Cu is highly reactive at high temperature, and therefore, when bonded to Al at high temperature, it is easy to form an oxide or an intermetallic compound of Al—Cu, which inhibits bonding. Sufficient bonding strength cannot be obtained.

  In order to solve such a problem, the present inventors have previously described, “When an Al member and a Cu member are joined, an Ag layer is formed as an insert layer on the joining surface of the Cu member. An invention relating to a “joining method and joining structure of an Al member and a Cu member characterized by brazing the Ag layer and the joining surface of the Al member” has been proposed (see Japanese Patent Application No. 2002-321182).

  However, as mentioned above, when the downsizing, thinning, weight reduction, and high performance of products in the electronic equipment industry become significant, various types of products can be applied to enable precision parts. Therefore, excellent dimensional characteristics are required for heat exchange devices and heat transfer devices.

  Here, as dimensional characteristics required for heat exchange equipment and heat transfer equipment, not only the dimensional accuracy of equipment but also dimensional applicability associated with diversification of dimensions adopted by equipment can be cited. Therefore, it is necessary for the previously proposed Al-Cu bonded structure to have excellent dimensional characteristics as well.

  The present invention has been made in view of the dimensional characteristics required for the heat exchange device and the heat transfer device described above, and secures a member having an Al—Cu dissimilar material joint excellent in workability, which is obtained by rolling. By performing the thinning process, it has excellent dimensional accuracy and can cope with the dimensional applicability accompanying the diversification of dimensions, and also has the lightness of Al and the heat transfer, thermal diffusivity, and corrosion resistance of Cu. It is an object of the present invention to provide a thin Al—Cu bonded structure and a method for manufacturing the same.

  In order to solve the above-described problems, the present inventors have conducted detailed studies on the bonding strength, deformation behavior, and workability of various Al—Cu bonding members.

  FIG. 1 is a diagram schematically showing a typical structure of a joint in a dissimilar material joint in which Al—Cu is brazed directly using an Al—Si brazing material. The bonding conditions at this time are Al—Si—Mg—Bi brazing material, brazing temperature of 530 ° C. (803 K), and brazing time of 60 sec.

  As shown in the figure, the formation of two types of intermetallic compounds, a δ phase formed in a layer form and an amorphous θ phase, is observed at the Al—Cu joint, both of which are made of Al—Cu. It is an intermetallic compound.

  Further, according to the result of the shear fracture test of the brazed joint, the deformation fracture of the joint exhibits brittle behavior and hardly undergoes deformation of the base material. Specifically, deformation fracture occurs at the joint, and the tensile strength of the joint remains at about 12.5 Mpa, which is a significantly lower value than the tensile strength of 65 Mpa of the base material Al (industrial pure Al). It has become.

  FIG. 2 is a diagram schematically showing a representative structure of a joint portion in which Ag is inserted as an insert material into an Al—Cu joint surface using an Al—Si based brazing material and different materials are joined. The joining conditions at this time were an Al—Si—Mg—Bi alloy brazing material, a brazing temperature of 550 ° C. (823 K), and a brazing time of 600 seconds.

  According to the binary equilibrium diagram of Ag—Cu, this combination is a typical eutectic reaction system, formation of intermetallic compounds is not observed in all composition ranges, and the eutectic point temperature is 779 ° C. And high temperature. For this reason, no structural change is observed in the Cu-Ag joint due to brazing, and the reaction of Al and Cu and the formation of fragile intermetallic compounds due to the reaction are not observed.

  On the other hand, the reaction region in the Ag-Al junction has a complicated form and is classified into four regions as shown in the schematic diagram of FIG. A first phase of an amorphous phase is generated at the reaction interface between the brazing filler metal and Ag, and a second phase consisting of a massive generated phase is recognized in the first phase. From the first phase to the brazing filler metal side, a plate-like product is generated in the form of a mesh in the fourth phase to constitute the third phase.

According to elemental analysis by an X-ray microanalyzer (EPMA), the first phase and the third phase are Ag ₂ Al which is an intermetallic compound of Al and Ag. The second phase is Si contained in the brazing material, and the fourth phase is Al in the brazing material.

  When the shear fracture test of the brazed joint is performed, the deformation behavior shows ductile fracture in the base material Al region, and the tensile strength of the joint is equivalent to that of the base material Al. Compared to brazed joints, the strength is dramatically improved.

  Thus, by inserting Ag as an insert material into the Al-Cu joint surface and brazing, the strength and deformation behavior of the brazed joint are equivalent to that of the base material Al, and it is ductile. It is mainly in the base material Al region that a large fracture occurs.

  On the other hand, with the downsizing, thinning, lightening, and high performance of electronic equipment, in order to exhibit excellent dimensional characteristics, cold rolling or hot rolling is performed to reduce the thickness of the rolled material. It is effective to perform processing. That is, a predetermined dimensional accuracy can be ensured by performing a cold or hot rolling process. Furthermore, since a predetermined equipment dimension can be adopted by setting the processing rate as appropriate according to the final target dimension required, it is possible to meet the required dimension applicability.

  The deformation behavior of the Al—Cu bonding member described above is equivalent to that of the base material Al, and ductile fracture occurs mainly in the base material Al region. Therefore, the conventional rolling process of the Al material can be applied to the Al—Cu bonded member, and thereby an Al—Cu bonded structure material excellent in dimensional characteristics can be manufactured.

  In rolling the Al—Cu joint member, it is important to suppress the deterioration of deformability due to work hardening and the like and the growth of intermetallic compounds in the joint. When thinning is performed by cold rolling, growth of an intermetallic compound is suppressed, but deformability of the member is lowered by work hardening, and it is difficult to perform sufficient thinning. For this reason, it is necessary to perform heat treatment for each cold rolling to recover the deterioration of deformability due to work hardening or the like.

  On the other hand, if the hot working can be performed in a temperature range in which the growth of the intermetallic compound can be suppressed and the deformability is not deteriorated, it is not necessary to perform a heat treatment again every processing. From such a point of view, it is desirable to reduce the thickness by hot rolling in rolling the Al—Cu bonding member.

The present invention has been completed on the basis of the above findings, and the gist of the present invention is the following (1) thin Al—Cu bonded structure and (2) a method for manufacturing a thin Al—Cu bonded structure.
(1) A thin Al—Cu joint structure obtained by rolling a brazed joint member using Ag as an insert material on a joint surface between an Al member and a Cu member.

The thin Al—Cu bonded structure has a thickness of 0.1 mm or more, and it is desirable to reduce the thickness of the brazed bonded member by hot rolling.
(2) A method for producing a thin Al—Cu joint structure, characterized in that rolling processing is performed on a joining surface between an Al member and a Cu member, using a brazing joint member using Ag as an insert material as a starting material.

  In the manufacturing method of the thin Al—Cu bonded structure, hot rolling is performed at 350 ° C. to 500 ° C., and when the hot rolling is repeated, the rolling reduction in each rolling is set to 20% ± 10%, It is desirable to perform annealing after finishing the hot rolling.

The “brazing” employed in the present invention is not particularly limited in terms of conditions, and any method that is usually used for Al—Ag bonding may be used. In order to stably form Ag ₂ Al, which is an intermetallic compound of Al—Ag, at the brazed joint, it is desirable to use an Al—Si based brazing material. Among the brazing materials, Al—Si—Mg— It is further desirable to use a Bi-based alloy braze.

  The “rolling process” employed in the present invention applies cold and hot rolling methods and conditions conventionally used as an Al rolling method, and particularly limits rolling equipment, rolling conditions, etc. is not.

  According to the manufacturing method of the present invention, by securing a member having an Al—Cu dissimilar material joint excellent in workability and reducing the thickness by rolling, it has excellent dimensional accuracy and diversification of dimensions. It is possible to manufacture a thin Al—Cu bonded structure that can cope with the dimensional applicability associated with. This thin Al-Cu bonded structure combines the lightness of Al with the heat transfer, thermal diffusivity, and corrosion resistance of Cu, and demands for smaller, thinner, lighter, and higher performance electronic devices. It can correspond to.

The present invention relates to a thin Al-Cu bonded structure obtained by rolling an Al-Cu bonded member and a method for manufacturing the same, and the contents are divided into the workability of the Al-Cu bonded member and the rolling process. To do.
1. Workability of Al—Cu bonding member As shown in FIG. 2, when brazing using an Al—Si brazing material, Ag is inserted into the Al—Cu bonding surface as an insert material to perform dissimilar material bonding. As a result, the initial Ag remains in the brazed portion, which has a suitable effect on the workability of the Al—Cu bonded member. The operation is as follows.

  The first is to inhibit the direct reaction of Al—Cu by allowing the Ag layer to remain in the brazed Al—Cu joint. Thereby, generation | occurrence | production of (delta) phase and (theta) phase which are harmful intermetallic compounds by Al-Cu can be suppressed.

Secondly, by leaving the Ag layer in the initial stage of the brazing reaction, it is possible to promote the formation of Ag ₂ Al, which is an intermetallic compound of Ag—Al, in a network form and maintain this formation promotion. it can.

In general, an intermetallic compound is brittle, and Ag ₂ Al is expected to exhibit low strength in the same way as the δ phase and the θ phase, which are Al—Cu intermetallic compounds, in view of its hardness. However, since Ag ₂ Al is formed in a form dispersed in the surrounding Al in the surrounding Al, even if a part of it is broken, the entire Al is not immediately destroyed, and the ductility of the surrounding Al Based on the deformation behavior, ductile deformation is shown. For this reason, the strength of the joint portion can show the same strength as that of the base material Al.

Furthermore, Ag ₂ Al, which is an intermetallic compound of Ag—Al, also affects the stress distribution state of the joint. According to the analysis by the present inventors, in the Al—Cu direct bonding portion shown in FIG. 1, a stress concentration portion having the largest maximum principal stress is generated inside the θ phase due to the tensile load.

On the other hand, in the joint portion using the Ag insert material shown in FIG. 2, a stress concentration portion of the maximum principal stress is generated at the intersection of the mesh Ag ₂ Al. For this reason, there is no particularly conspicuous stress concentration portion in the surrounding Al, and a substantially uniform distribution state is obtained.

  For this reason, when comparing the deformation behavior of the two, the Al—Cu direct joint shown in FIG. 1 breaks starting from the stress concentration part of the maximum principal stress generated in the θ phase due to the tensile load. Propagates instantly and leads to destruction.

On the other hand, in the joint shown in FIG. 2, that is, the joint where Ag is inserted as the insert material into the Al—Cu joint surface, similarly, the Ag formed in a mesh shape in the third phase by the tensile load. _{2 Although} stress concentration occurs in Al, even if local fracture occurs here, it does not show any behavior that leads to instantaneous fracture, the tensile load is borne by the surrounding Al, and ductile deformation behavior is exhibited. I will take it.

  FIG. 3 is a diagram showing the relationship between the tensile strength of the Al—Cu bonding member and the brazing time when the brazing temperature is used as a parameter. The brazing temperature is changed in the range of 813K to 830K (540 ° C to 557 ° C).

  At a brazing temperature of 813 K (540 ° C.), a sufficient liquid phase was not generated at the joint, and brazing could not be performed. Therefore, the fracture was brittle with almost no deformation of the base material during all brazing times. Moreover, all the breaking positions were brazed portions, and the tensile strength was an extremely low value of about 15 Mpa on average.

  Further, when the brazing temperature is 830 K (557 ° C.), the base material Al melts violently, the joint shows brittle deformation behavior without base material deformation, and the fracture position is the brazed part. .

  In contrast, when the brazing temperatures are 818K (545 ° C) and 823K (550 ° C), the tensile strength of the joint is 65 Mpa and the tensile strength of the base material Al when the brazing time is 1800 sec or less. Some of them break down on the base material Al side. In addition, it is accompanied by a large deformation of the base material before the destruction, and after exhibiting a ductile deformation behavior, it has been destroyed.

Therefore, in the brazed joint member using Ag as an insert material on the joint surface between the Al member and the Cu member, by setting an appropriate holding time together with an appropriate brazing temperature range, the Al-Cu joint surface Therefore, an effective Ag layer can be left. Thereby, ductile deformation behavior is exhibited, the strength of the joint portion can be ensured as high as that of the base material Al, and excellent workability can be exhibited, so that it can be used as a work material in rolling.
2. Rolling of Al—Cu Joining Member In the manufacturing method of the present invention, the Al—Cu joining member is thinned by either cold or hot rolling. In this case, if hot rolling is performed in a temperature range necessary for recovering the reduced mechanical properties of Al, a heat treatment for recovering the reduced strength for each rolling process becomes unnecessary.

  For this reason, in the rolling process employed in the present invention, it is desirable to employ hot rolling, but the processing temperature at this time needs to be equal to or lower than a temperature at which the growth of the intermetallic compound at the joint can be suppressed.

  In the present invention, in order to repeat hot working stably, it is desirable that the working temperature is 350 ° C. to 500 ° C. If the processing temperature is lower than 350 ° C., the lowered deformability may not be sufficiently recovered, and a new heat treatment may be required.

  On the other hand, it is desirable to set the upper limit of the processing temperature to 500 ° C. When rolling above 500 ° C., the thickness of the remaining Ag layer may decrease sharply due to the significant activation of the growth of the first phase in FIG. 2, and further repeating the rolling, This is because the Ag layer eventually disappears, and a harmful Al—Cu intermetallic compound may be formed by a direct reaction between Al and Cu.

  In the production method of the present invention, the thickness of the Al—Cu bonded structure can be selected to a minimum of 0.1 mm after the rolling process in order to ensure dimensional applicability. In this case, the processing schedule in the rolling process is set based on the final target dimension, but when hot rolling is repeated, the reduction ratio in each rolling is set to 20% ± 10%. desirable. However, the rolling reduction (Rd) is expressed by (thickness before processing−thickness after processing) / (thickness before processing) × 100%.

  Furthermore, in the manufacturing method of the present invention, it is desirable to perform annealing after finish rolling. This is for recovering the mechanical properties of Al lowered by the rolling process, restoring the mechanical properties of the thin Al-Cu bonded structure, and stabilizing the strength. The annealing after finish rolling is based on the processing conditions of 400 ° C. × 30 minutes.

  The thin Al-Cu joined structure of the present invention has excellent dimensional accuracy by rolling the Al-Cu joined member described above, and can cope with dimensional applicability accompanying diversification of dimensions, It can have both the lightness of Al and the heat conductivity, thermal diffusivity, and corrosion resistance of Cu, and can be suitably used as a heat exchange material and a heat dissipation material.

The effects of the thin Al—Cu bonded structure and the manufacturing method thereof according to the present invention will be described based on specific examples.
(1) Production of Al-Cu bonding member The base material Al used in the examples is commercially available pure aluminum (A1050), and pure silver foil (purity 99.99%) is used as Ag used in the insert material. A commercially available Ag clad Cu plate (Ag thickness: 100 μm, Cu thickness: 3 mm) clad with oxygen-free steel (C1020) was used.

First, in order to form an insert layer on the surface of the base material Cu, the surface of the base material Cu is mirror-finished, and then a 100 μm thick Ag foil is placed in contact with the surface of the base material Cu. Solid phase diffusion treatment was performed. The diffusion conditions at this time were a diffusion temperature of 765 ° C. (1038 K), a diffusion time of 5 hours, and a contact load of 2.54 MPa. In diffusion bonding, a hydraulic pressure was used for pressurization in a vacuum of 5 × 10 ⁻³ Torr.

  The brazing material is a commercially available Al-10Si-1.5Mg-0.1Bi based brazing foil (corresponding to 4104, solidus temperature: 559 ° C. (832 K), liquidus temperature: 591 ° C. (864 K), thickness: 100 μm), the insert layer and the base material Al (Al thickness: 3 mm) were brazed.

At the time of joining, the joint surfaces are sufficiently degreased with acetone, 0.294 MPa is added with a spring, and the inside of the furnace is 10 minutes at a joining temperature of 550 ° C. (823 K) in a vacuum of 3 × 10 ⁻³ Torr. It was brazed. The dimension of the Al—Cu joined member after brazing was 6 mm thick, and the ratio was approximately Cu thickness: 3 mm and Al thickness: 3 mm.
(2) Rolling process and bonded structure Using the obtained Al-Cu bonded member as a starting material, hot rolling was performed many times to produce a thin Al-Cu bonded structure having a final thickness of 0.8 mm. . The processing temperature of hot rolling was 400 ° C., and the rolling reduction in each rolling was 20%.

  The specific processing schedule is as follows: Total thickness 6 mm → 4.8 mm (Rd: 20%) → 3.84 mm (Rd: 20%) → 3.07 mm (Rd: 20%) → 2.46 mm (Rd: 20%) ) → 1.97 mm (Rd: 20%) → 1.58 mm (Rd: 20%) → 1.26 mm (Rd: 20%) → 1.0 mm (Rd: 21%) → 0.8 mm (Rd: 20%) ), 9 times of hot rolling was repeated. After finishing the final thickness to 0.8 mm by hot rolling with a total reduction rate of 87%, annealing was performed under conditions of 400 ° C. × 30 minutes.

  FIG. 4 is a diagram showing the result of SEM observation of the structure of the joint after finishing to a thickness of 0.8 mm by hot rolling. As shown in the figure, the joining portion is composed of a base material Cu, an Ag layer, an Ag—Al reaction region, and a base material Al from the right side of the drawing. The Ag layer had a thickness of 100 μm before the treatment, but the layer thickness remaining after the joining treatment was 5 to 8 μm. In addition, the base material Cu and the base material Al also showed a uniform thickness reduction according to the rolling reduction.

  Although the reaction region takes a complicated form, as shown in the schematic diagram of FIG. 2, the first to fourth phase formation forms obtained with the Al—Cu bonding member as a starting member are provided as they are. I understand that. Even after finishing to a wall thickness of 0.8 mm, no defects or the like were observed in any of the base material Cu, base material Al, Ag layer, and reaction region of the joint.

  Furthermore, it is subjected to the same hot rolling over many times to reduce the thickness to a final thickness of 0.1 mm, and in any of the reaction regions of the base material Cu, base material Al, Ag layer and Ag-Al. It has been confirmed that the thin Al—Cu bonded structure of the present invention can be manufactured without any defects.

  According to the thin Al—Cu joint structure and the manufacturing method of the present invention, excellent dimensional accuracy is obtained by securing a member having an Al—Cu dissimilar material joint having excellent workability and reducing the thickness by rolling. In addition, it can cope with dimensional applicability accompanying diversification of dimensions. The resulting thin Al-Cu bonded structure has both the lightness of Al and the heat transfer, thermal diffusivity, and corrosion resistance of Cu, making electronic devices smaller, thinner, lighter, and higher performance. Therefore, it can be widely used as a heat exchange material or a heat transfer material.

It is the figure which showed typically the typical structure | tissue of the junction part in the dissimilar material joining which brazed Al and Cu directly using the Al-Si type brazing material. It is the figure which showed typically the typical structure | tissue of the junction part in the dissimilar material joining which inserted Ag as an insert material in the joining surface of Al-Cu using the Al-Si type brazing material. It is a figure which shows the relationship between the tensile strength of an Al-Cu joining member when brazing temperature is made into a parameter, and brazing time. It is a figure which shows the result of having observed the structure of the junction part after finishing to thickness 0.8mm by hot rolling by SEM.

Claims (8)

  A thin Al-Cu joint structure obtained by rolling a brazed joint member using Ag as an insert material on a joint surface between an Al member and a Cu member.   The thin Al-Cu joint structure according to claim 1, wherein the brazed joint member is processed by hot rolling.   The thin Al-Cu bonded structure according to claim 1 or 2, wherein the thickness of the structure is 0.1 mm or more.   A method for producing a thin Al-Cu joint structure, characterized in that rolling is performed using a brazed joint member using Ag as an insert material on a joint surface between an Al member and a Cu member.   A method for producing a thin Al-Cu bonded structure, wherein the processing is performed by hot rolling.   The method for producing a thin Al-Cu bonded structure according to claim 5, wherein the hot rolling is performed at 350C to 500C.   The method for producing a thin Al-Cu bonded structure according to claim 5 or 6, wherein when the hot rolling is repeated, the rolling reduction in each rolling is 20% ± 10%. The method for producing a thin Al-Cu bonded structure according to any one of claims 4 to 7, wherein annealing is performed after finishing the hot rolling.

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